Electrochemical plating cell having a diffusion member

ABSTRACT

Embodiments of the invention provide an electrochemical plating cell that is divided by an ionic membrane into an anolyte volume and a catholyte volume. The anolyte volume of the plating cell includes an electrically resistive diffusion member and an anode positioned therein. The catholyte volume of the cell is generally configured to receive a substrate for plating.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. provisional patent applicationSer. No. 60/515,465, filed Oct. 29, 2003, which is herein incorporatedby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention generally relate to a flow controlmember for an electrochemical plating cell.

2. Description of the Related Art

Metallization of sub 100 nanometer features is a foundational technologyfor present and future generations of integrated circuit manufacturingprocesses. More particularly, in devices such as ultra large scaleintegration-type devices, i.e., devices having integrated circuits withmore than a million logic gates, the multilevel interconnects that lieat the heart of these devices are generally formed by filling highaspect ratio, i.e., greater than about 15:1, interconnect features witha conductive material, such as copper. Conventional depositiontechniques, such as chemical vapor deposition (CVD) and physical vapordeposition (PVD) have been unsuccessful in filling features of thissize, and as such, plating techniques, i.e., electrochemical plating(ECP) and electroless plating, have emerged as promising processes forvoid free filling of sub 100 nanometer sized high aspect ratiointerconnect features in integrated circuit manufacturing processes.

Conventional electrochemical plating cells contain an electrolyte baththat has an anode member positioned in a lower portion of the bath. Asubstrate to be plated is positioned in the electrolyte bath and anelectrical bias is applied between the anode and the substrate surfaceto drive the plating process. Conventional plating cells may alsoinclude a membrane and/or a resistive diffusion member positioned acrossthe fluid basin that holds the electrolyte solution. In recent platingcells, the cell basin has been divided into an anode compartment (alsoknown as an anolyte compartment) and a cathode compartment (also knownas a catholyte compartment) via use of a fluid isolation or ionicmembrane. In these plating cells the diffusion member is positioned inthe cathode compartment between the membrane and the substrate beingplated and is used to control the electrolyte flow toward the substratebeing plated.

However, positioning of the diffusion member in the catholytecompartment has been shown to contribute to defects in the plated copperlayers. More particularly, positioning of the diffusion member in thecatholyte solution has been shown to increase the likelihood of formingbubbles in the solution, which travel to the substrate surface and causedefects. Additionally, the diffusion members are generally manufacturedfrom an electrically resistive material, and as such, the diffusionmember presents challenges to plating a uniformly thick copper layeronto a thin seed layer that also has a substantially high resistivity.Further, the positioning of the flow control member in the catholyte hasbeen shown to contribute to undesirable terminal effect platingcharacteristics.

Therefore, there is a need for a plating cell configured to eliminatethe challenges associated with positioning a diffusion member in thecatholyte portion of a plating cell.

SUMMARY OF THE INVENTION

Embodiments of the invention provide an electrochemical plating cellthat is divided by an ionic membrane into an anolyte volume and acatholyte volume. The anolyte volume of the plating cell includes anelectrically resistive diffusion member and an anode positioned therein.The catholyte volume of the cell is generally configured to receive asubstrate for plating.

Embodiments of the invention further provide a plating cell having ananode compartment and a cathode compartment separated by an ionicmembrane. An anode is positioned in a lower portion of the anodecompartment and a flow control member is positioned above the anode inthe anode compartment. The flow control member is generally a diskshaped member having a first thickness on a first side and a secondthickness on a second opposing side, wherein the second thickness isdifferent from the first, thus generating a wedge shaped member. Themembrane is generally positioned at a tilt angle with respect to theupper surface of the anode, and further, the membrane tilt angle isgenerally opposite of a tilt angle of an upper surface of the flowcontrol member.

Embodiments of the invention may further provide an electrochemicalplating cell. The plating cell generally includes a fluid basin having afluid outlet, a membrane positioned across the fluid basin, the membraneseparating the fluid basin into a catholyte volume and an anolytevolume, an anode positioned in the anolyte volume, and a diffusionmember positioned in the anolyte volume.

Embodiments of the invention may further provide an electrochemicalplating cell. The plating cell generally includes a cell body defining afluid processing volume and having an opening configured to receive asubstrate for processing, a cationic membrane positioned across thefluid processing volume and separating the fluid processing volume intoa catholyte volume and an anolyte volume, an anode positioned in theanolyte volume, and an electrically insulative fluid permeable diffusionmember positioned across the fluid processing volume between the anodeand the cationic membrane.

Embodiments of the invention may further provide a plating cell having afluid basin having an opening configured to receive a substrate forprocessing, a copper anode positioned in a lower portion of the fluidbasin, a porous electrically insulative diffusion member positionedacross the fluid basin at a position between the anode and the opening,and a cationic membrane positioned across the fluid basin at a positionbetween the diffusion member and the opening.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 illustrates a plan view of an exemplary plating system of theinvention.

FIG. 2 illustrates a sectional view of an exemplary plating cell of theinvention.

FIG. 3 illustrates a sectional view of another embodiment of theexemplary plating cell of the invention.

FIG. 4 illustrates a sectional view of a third embodiment of theexemplary plating cell of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates a top plan view of an exemplary ECP system 100 of theinvention. ECP system 100 includes a factory interface 130, which isalso sometimes referred to as a substrate loading station. Factoryinterface 130 includes a plurality of cassette receiving stationsconfigured to interface with substrate containing cassettes 134. A robot132 is positioned in factory interface 130 and is configured to accesssubstrates contained in the cassettes 134. Further, robot 132 alsoextends into a link tunnel 115 that connects factory interface 130 toprocessing mainframe or platform 113. The position of robot 132 allowsthe robot to access substrate cassettes 134 to retrieve substratestherefrom and then deliver the substrates to one of the processing cells114,116 positioned on the mainframe 113, or alternatively, to anannealing station 135. Similarly, robot 132 may be used to retrievesubstrates from the processing cells 114,116 or the annealing chamber135 after a substrate processing sequence is complete. In this situationrobot 132 may deliver the substrate back to one of the cassettes 134 forremoval from system 100.

The processing mainframe 113 includes a substrate transfer robot 120centrally positioned thereon. Robot 120 generally includes one or morearms/blades 122, 124 configured to support and transfer substratesthereon. Additionally, the robot 120 and the accompanying blades 122,124 are generally configured to extend, rotate, and vertically move sothat the robot 120 may insert and remove substrates to and from aplurality of processing locations 102, 104, 106, 108, 110, 112, 114, 116positioned on the mainframe 113. Similarly, factory interface robot 132also includes the ability to rotate, extend, and vertically move itssubstrate support blade(s), while also allowing for linear travel alongthe robot track that extends from the factory interface 130 to themainframe 113. Generally, process locations 102, 104, 106, 108,110,112,114, 116 may be any number of processing cells utilized in anelectrochemical plating platform. More particularly, the processlocations may be configured as electrochemical plating cells, rinsingcells, bevel clean cells, spin rinse dry cells, substrate surfacecleaning cells (which collectively includes cleaning, rinsing, etching,and ozone treatment cells, etc.), electroless plating cells, metrologyinspection stations, and/or other processing cells that may bebeneficially used in conjunction with a plating platform. Each of therespective processing cells and robots are generally in communicationwith a process controller 111, which may be a microprocessor-basedcontrol system configured to receive inputs from both a user and/orvarious sensors positioned on the system 100 and appropriately controlthe operation of system 100 in accordance with the inputs.

In the exemplary plating system 100 illustrated in FIG. 1, theprocessing locations may be configured as follows. Processing locations114 and 116 may be configured as an interface between the wet processingstations on the mainframe 113 and the dry processing regions in the linktunnel 115, annealing chamber 135, and the factory interface 130. Theprocessing cells located at the interface locations may be spin rinsedry cells and/or substrate cleaning cells, for example. Moreparticularly, each of locations 114 and 116 may include both a spinrinse dry cell and a substrate cleaning cell in a stacked configuration.Locations 102, 104, 110, and 112 may be configured as plating cells,either electrochemical plating cells or electroless plating cells, forexample. Locations 106, 108 may be configured as substrate bevelcleaning cells. Additional configurations and implementations of anelectrochemical processing system are illustrated in commonly assignedU.S. patent application Ser. No. 10/435,121 filed on Dec. 19, 2002entitled “Multi-Chemistry Electrochemical Processing System”, which isincorporated herein by reference in its entirety. Regardless of theconfiguration of the respective plating cells, ECP system 100 isgenerally configured to provide multiple plating cells on a singleplatform, wherein each of the multiple plating cells is capable ofhaving a different chemistry therein from each of the other platingcells on the platform.

FIG. 2 illustrates a partial perspective and sectional view of anexemplary plating cell 200 that may be implemented in processinglocations 102, 104, 110, and 112 (or other processing locations onsystem 100 as desired). The electrochemical plating cell 200 generallyincludes an outer basin 201 and an inner basin 202 positioned withinouter basin 201. Inner basin 202 is generally configured to contain aplating solution that is used to plate a metal, e.g., copper, onto asubstrate during an electrochemical plating process. During the platingprocess, the plating solution is generally continuously supplied toinner basin 202, and therefore, the plating solution continuallyoverflows the uppermost point (generally termed a “weir”) of inner basin202 and is collected by outer basin 201 and drained therefrom forchemical management and/or recirculation.

Plating cell 200 is generally positioned at a tilt angle, i.e., a frameportion 203 of plating cell 200 is generally elevated on one side suchthat the components of plating cell 200 are tilted between about 3° andabout 30° from horizontal, or generally between about 4° and about 10°.The frame member 203 of plating cell 200 supports an annular base member204 on an upper portion thereof, and since frame member 203 is elevatedon one side, the upper surface of base member 204 is generally tiltedfrom the horizontal at an angle that corresponds to the tilt angle offrame member 203 relative to a horizontal position. However, embodimentsof the invention are not limited to tilted plating cells, as positioningthe plating cell 200 at any angle with respect to horizontal, including0°, for example, is contemplated within the scope of the invention.

Base member 204 generally includes an annular or disk shaped recessformed into a central portion thereof, the annular recess beingconfigured to receive a disk shaped anode member 205 therein. Basemember 204 further includes a plurality of fluid inlets/drains 209extending from a lower surface thereof. Each of the fluid inlets/drains209 are generally configured to individually supply or drain a fluid toor from either the anode compartment or the cathode compartment ofplating cell 200 via conduits (not shown) formed through the base member204. Anode member 205 generally includes a plurality of slots 207 formedtherethrough, wherein the slots 207 are generally positioned in parallelorientation with each other across the surface of the anode 205. Theparallel orientation allows for dense fluids generated at the anodesurface to flow downwardly across the anode surface and into one of theslots 207. However, embodiments of the invention are not limited toslotted-type anodes, as various other anodes, including solid disk-typeanodes and other anodes conventionally used in electrochemical plating,are contemplated within the scope of the invention.

Plating cell 200 further includes a membrane support assembly 206.Membrane support assembly 206 is generally secured at an outer peripherythereof to base member 204, and includes an interior region configuredto allow fluids to pass therethrough. A membrane 208 is stretched acrossthe support 206 and generally operates to fluidly separate a catholytechamber (positioned adjacent the substrate being plated) and anolytechamber (positioned adjacent the anode electrode in the cell) of theplating cell. The membrane support assembly 206 may include an o-ringtype seal positioned near a perimeter of the membrane 208, wherein theseal is configured to prevent fluids from traveling from one side of themembrane 208 secured on the membrane support 206 to the other side ofthe membrane 208. As such, membrane 208 generally provides fluidisolation between the anode and cathode portions of the plating cell200, i.e., via use of a cationic membrane. Exemplary membranes that maybe used to fluidly isolate an anolyte from a catholyte are illustratedin commonly assigned U.S. patent application Ser. No. 10/627,336 filedon Jul. 24, 2003 entitled “Electrochemical Processing Cell”, which ishereby incorporated by reference in its entirety. Alternatively,membrane 208 may be a fluid permeable filter-type membrane that allowsfluid to pass therethrough.

A diffusion plate 210, which is generally a porous ceramic disk memberor other fluid permeable electrically resistive member is positioned inthe cell between anode 205 and the membrane 208. The positioning of thediffusion member 210 below the membrane 208 is a departure fromconventional plating cells where the diffusion member would generally bepositioned above the membrane 208 adjacent the substrate being plated.When the diffusion member 210 is placed below the membrane 208, it doesnot generate substantially laminar flow of electrolyte toward theplating surface, as with conventional plating cells having the diffusionmember above the membrane. The inventors have concluded that asubstantially laminar flow may not be necessary, as the platingthickness or uniformity is predominantly controlled by the electricfield and boundary layer thickness, and not the fluid flow at theplating surface, as previously thought. The boundary layer thickness atthe substrate is driven mostly by the relative motion of the wafer andfluid induced by rotation of the substrate during the plating process.Put simply, the inventors profess that the uniformity of a platingprocess is affected by the electric field primarily, then therotationally induced boundary layer, then the vertical flow inducedboundary layer, in that order. As such, by the time variations in thevertical fluid flow are considered, the impact on the uniformity is athird or even fourth order effect.

However, there still is a benefit to a implementing a diffuser in aplating cell. That benefit is that it increases the cell electricalimpedance, and in doing so, reduces the percentage increase in the cellvoltage as the soluble anode erodes, and in effect, moves away from thesubstrate. To this end, if the diffuser thickness is doubled, theuniformity decreases with a single “standard” thickness, and if it istaken away, the uniformity, except at the very edge, improves. The edgeeffect is E-field driven, which is fixed by other techniques. In thecase of this invention, the diffuser has the additional task ofcompensating for the difference in anolyte and catholyte conductivities,the path length for which is varying as a result of the tilt in themembrane relative to the workpiece. Further still, positioning thediffuser in the catholyte serves as a bubble trap, which has been shownto contribute to undesirable plating defects.

With the diffuser 210 positioned below the membrane 208, the diffusionmember 210 is positioned in the anolyte solution, i.e., the solutionflowing below the membrane 208 that does not include plating additivesand that does not contact the plating surface of the substrate beingplated. The diffusion member 210 is generally manufactured from anelectrically insulating material, and as such, the diffusion member 210also operates to control the electric field generated between the anodeand the substrate. In conventional plating cells, and in someembodiments of the invention, the diffusion member 210 is a disk shapedmember having a uniform thickness across the surface thereof.

However, in plating cell configurations wherein the upper surface of theanode 205 and the surface of the membrane 208 are not positioned inparallel relationship with each other, as will be further discussedherein, the diffusion member 210 may be configured to have a varyingthickness across the surface thereof. More particularly, the thicknessof the diffusion member 210 may be varied to compensate for variances inthe resistance path between the anode 205 and the substrate beingplated, such that the perpendicular line resistance between the anode205 and the substrate being plated remains constant across all points onthe surface of the substrate. Additionally, with regard to the type ofthe diffusion member 210 described above, embodiments of the inventionare not intended to be limited to ceramic diffusion members, as otherelectrically insulative fluid permeable (porous) materials that arenon-reactive with electrochemical processing fluids may also be used inembodiments of the invention without departing from the scope thereof.Additionally, embodiments of the invention further contemplate thatelectrically insulative materials that are not porous may also be usedin embodiments of the invention, ie., as holes or bores may be formedthrough the electrically insulative material to allow fluid to flowtherethrough in a manner similar to the fluid flow through the abovenoted porous diffusion member.

When a porous diffusion member is implemented in embodiments of theinvention, then the porosity of the diffusion member 210 may be betweenabout 20% and about 60%, and more particularly, between about 30% andabout 50%. These porosities have been shown to generate a resistivitywhen wet with electrolyte that is between about three and ten timesgreater or higher than the resistivity of the same shape of cell withoutthe diffusion member 210 positioned therein. The thickness of thediffusion member 210 may be between about 1 mm and about 30 mm, forexample, for a disk shaped or uniform thickness diffusion member 210,which has also shown improved plating characteristics when platingmaterial onto thin seed layers, i.e., seed layers having a thickness ofless than about 500 Å.

Further, positioning of the diffusion member 210 in the anolytesolution, e.g., below the membrane 208, assists with minimizing bubblespresent at the substrate surface and removes the diffusion member as apossible source for surface defects on the substrate. Additionaladvantages of positioning the diffusion member 210 in the anolyteinclude improved terminal effect results and an improved ability tocounteract the local variations in the resistivity of the membrane 208and the anode 205. The positioning of the diffusion member 210 betweenthe membrane 208 and the anode 205 also allows for the plating cell tobe positioned vertically instead of tilted, which may mitigate immersiondefects.

Additional embodiments of the exemplary plating cell illustrated in FIG.2 are illustrated in commonly assigned U.S. patent application Ser. No.10/268,284 which was filed on Oct. 9, 2002 under the title“Electrochemical Processing Cell”, claiming priority to U.S. ProvisionalApplication Ser. No. 60/398,345 which was filed on Jul. 24, 2002, bothof which are incorporated herein by reference in their entireties.Additional embodiments of the plating cell are also illustrated incommonly assigned U.S. patent application Ser. No. 10/627,336 filed onJul. 24, 2003 entitled “Electrochemical Processing Cell”, which is alsoincorporated by reference herein in its entirety.

FIG. 3 illustrates another embodiment of the plating cell of theinvention. In this embodiment the plating cell 300 may be positionedhorizontally, at a tilt angle, or vertically. An anode 305 is positionedin a lower portion of the cell 300 and includes a generally planar uppersurface. A diffusion member 310 is positioned above the anode 305 and acentral plane of the diffusion member 310 plane (a central plane that isequidistant from both outer surfaces of the diffusion member), andfurther, the central plane is generally parallel to the upper surface ofthe anode 305. The thickness of the diffusion member 310 generallyvaries from one side to the other in one direction, which generallygenerates a wedge shaped disk member. A membrane support 306 and amembrane 308 are positioned above the diffusion member 310. The membrane308 is generally positioned at a tilt angle, i.e., the membrane 308 isgenerally positioned at an angle with respect to horizontal or at anangle with respect to the upper surface of the anode. The tilt angle isgenerally between about 5° and about 30°, or more particularly, betweenabout 5° and about 15°. The membrane 308 is generally an ionic membrane,and more particularly, a cationic membrane, for example. The remainingcomponents of plating cell 300 are generally similar to the componentsof the plating cell illustrated in FIG. 2, i.e., frame 303, basins 301and 302, fluid inlets 309, anode slots 307, and anode base 304.

In the embodiment of the invention illustrated in FIG. 3, the diffusionmember 310 is generally positioned such that the thicker side of thediffusion member 310 is positioned on the same side of the plating cellas the lowermost portion of the membrane 308. More particularly, asillustrated in FIG. 3, the thicker side of the diffusion member 310 ispositioned on the left side of the plating cell 300, which correspondsto the side of the plating cell 300 where the membrane 308 is positionedat its lowest point, e.g., at the point closest to the anode 305.Generally, the thickness of the diffusion member 310 at the thickestportion is between about 6 mm and about 37 mm, while the thickness atthe thinnest portion is between about 1 mm and about 30 mm. As such, thediffusion member may be disk shaped, or wedge shaped with a surfaceangle that is between about 3° and about 15°, for example. Similarly,the tilt angle of the membrane 308 may be between about 3° and about15°, for example, and more particularly, between about 6° and about 12°.

The embodiment of the invention illustrated in FIG. 3 is generallyconfigured to generate an equal resistance path between the anode 305and the substrate being plated at all locations across the plating cell,regardless of the thickness of the diffusion member 310 or the distancethe membrane 308 is from the substrate or anode 305. Generally, this isaccomplished by having the membrane 308 being positioned closer to theanode 305 at cell locations where the diffusion member 310 is thicker.Similarly, the membrane 308 is positioned closer to the substrate(farther away from the anode 305) at locations in the cell where thediffusion member 310 is thinner. Thus, the inventors have determinedthat the perpendicular line resistance between the anode 305 and thesubstrate being plated is proportional to the ratio of the thickness ofthe diffusion member 310 to the distance the membrane 308 is from theanode. As such, as the thickness of the diffusion member 310 increases,the distance of the membrane 308 from the anode 305 decreases in orderto maintain an equal resistance path to the substrate from the anode305. The proportion that determines the line resistance is generallybased upon the concept that the anolyte and catholyte solutions eachhave different resistances or conductances (the anolyte is generallymuch more resistive than the catholyte), and as such, when the distancebetween the anode and the membrane is large, i.e., the anolyte is thick,then the diffusion member may be thin and the distance from the membraneto the substrate (the catholyte resistance) may be thin. The proportionbalances the ratio of the anolyte thickness, catholyte thickness, anddiffusion member thickness to generate an equal line resistance to thesubstrate at all points across the anode surface. Generally, thesubstrate is positioned in the plating cell in a manner such that thesurface of the substrate being plated is parallel to the upper surfaceof the anode 305.

Further, embodiments of the invention, and in particular, theembodiments of the invention illustrated in FIGS. 2 and 3, are generallyconfigured to use a diffuser having a porosity of about 40%, which isconfigured to generate a resistivity when wet with the electrolyte(anolyte) that is approximately five times higher than the same volumeand shaped cell without the diffuser 210. Therefore, the plating cellcan be positioned horizontally and the cationic membrane can be tiltedby about 10° from the upper surface of the anode. As a result thereof,the diffusion member can be positioned in the anolyte (as opposed to thecatholyte in conventional plating cells) and cut or manufactured with aslope of about 10° (the tilt) divided by 5 (the difference inresistivity), which yields a cut or manufacture slope of approximately2° relative to the slope of the opposing surface. Additionally, thethickness of the diffusion member may be increased, which facilitatesthinner seed layers being plated in the same amount of timeconventionally used to plate onto thicker seed layers, as the increasedresistance anolyte used on conjunction with the thick diffuser thereinhas a much higher resistivity than provided by conventional plating cellconfigurations, and even those conventional plating cells havingseparated anolyte and catholyte fluid regions or chambers. Further,positioning the diffuser in the anolyte increases the resistance for agiven thickness, which increases uniformity for thin seed plating,counteracts the terminal effect, and counteracts local variations inresistivity present in the membranes of the cell and the anode.

In another embodiment of the invention, which is illustrated in thegeneral sectional view of FIG. 4, a plating cell 400 includes a wedgeshaped diffusion member 410 and a tilted ionic-type membrane 408 insimilar fashion to FIG. 3. The ionic membrane 408 further includes afirst membrane stack 420 positioned on or adjacent to an upper sidethereof, i.e., the side positioned closest to the upper or open portionof plating cell 400 where a substrate is received for plating. The ionicmembrane 408 also includes a second membrane stack 430 positioned on oradjacent to a lower side thereof, i.e., the side positioned closest tothe lower portion of the plating cell 400 where the anode 405 ispositioned. A third membrane stack 440 is positioned on or adjacent tothe upper surface of the anode 405 below the ionic membrane 408.

The ionic membrane 408 is generally a cationic membrane configured toallow positively charged ions, such as Cu²⁺ to travel upward through themembrane 408 from the anode 405 to the substrate being plated, whilepreventing plating solution additives and other constituents fromtraveling downward through the membrane from the catholyte solution intothe anolyte solution where they may contact the anode 405 and breakdown.Exemplary ionic membranes that may be used in embodiments of theinvention are described in commonly assigned U.S. patent applicationSer. No. 10/616,044 filed on Jul. 8, 2003 entitled “Anolyte for CopperPlating”, which is hereby incorporated by reference in its entirety.

The first membrane stack 420 generally includes a first membrane 421positioned adjacent the ionic membrane 408 and a second membrane 422positioned above the first membrane 421, such that the first membrane421 is positioned between the second membrane 422 and the ionic membrane408. The first membrane 421 is generally a hydrophilic fluid permeablemembrane having a thickness of between about 50 μm and about 150 μm andhaving pores sized (diameter) between about 2 μm and about 20 μm, forexample. The first membrane 421 is generally positioned immediatelyabove the ionic membrane 408 with only a minimal fluid passage spacepositioned between the two membranes. The second membrane 422 isgenerally positioned immediately above the first membrane 421, againwith a fluid passage space separating the membranes. The second membrane422 generally has a thickness of between about 30 μm and about 175 μmand includes pores sized between about 1 μm and about 15 μm, forexample. The outer perimeter of the first and second membranes 421, 422is sealably attached to a sidewall 401 of the plating cell 400. Thefluid space between the ionic membrane 408 and the first membrane 421includes a catholyte fluid drain 425 positioned in communicationtherewith, while the fluid space positioned between the first and secondmembranes 421, 422 is sealably in communication with the sidewall 401 ofthe cell 400. The catholyte fluid drain 425 is also in fluidcommunication with a catholyte region 461 of the plating cell 400.Further, a corresponding catholyte supply 463 is in fluid communicationwith the catholyte region 461.

The second membrane stack 422 (positioned on the lower surface of theionic membrane 408) also includes a two layer membrane stack. Themembrane stack includes a first membrane 427 positioned adjacent theionic membrane 408 and a second membrane 428 positioned adjacent thefirst membrane 427, such that the first membrane 427 is positionedbetween the second membrane 428 and the ionic membrane 408. Both thefirst and second membranes 427, 428 are sealably attached to thesidewall 401 of the plating cell 400. Further, first membrane 427 ispositioned such that there is a fluid space positioned between the ionicmembrane 408 and the first membrane 427. Similarly, the second membrane428 is positioned such that there is a fluid space between the secondmembrane 428 and the first membrane 427. The fluid space between theionic membrane 408 and the first membrane 427 is in fluid communicationwith an anolyte drain 426. The first membrane 427 is generally ahydrophilic fluid permeable membrane having a thickness of between about50 μm and about 150 μm and having pores sized (diameter) between about 2μm and about 20 μm, for example. The second membrane 427 generally has athickness of between about 30 μm and about 175 μm and includes poressized between about 1 μm and about 15 μm, for example.

The third membrane stack 440 is positioned on the upper surface of theanode 405. The third membrane stack generally includes a first membrane441 and a second membrane 442. The first membrane 441 is generallypositioned next to the upper surface of the anode 405, with a fluidspace separating the anode 405 from the membrane 441. The secondmembrane 442 is positioned above the first membrane 441 and is separatedfrom the first membrane 441 by a fluid space. Both the first and secondmembranes 441, 442 are generally sealably attached to the sidewall 401of the plating cell 400, however, the fluid space between the firstmembrane 441 and the anode 405 includes an anolyte drain 428 positionedin fluid communication therewith. The anolyte drain 428 is alsogenerally in fluid communication with an anolyte region 460 of theplating cell 400. Further, an anolyte supply line 462 is in fluidcommunication with the anolyte region 460.

In operation, the embodiment of the invention illustrated in FIG. 2 isconfigured to plate a metal, e.g., copper layer onto a semiconductorsubstrate having a thin seed layer, e.g., less than about 500 Å thereon.In this embodiment of the invention a substrate to be plated ispositioned such that the plating surface, i.e., the seed layer, is incontact with a catholyte plating solution contained within the innerfluid basin 202. The catholyte plating solution is continually suppliedto the inner fluid basin 202 via at least one fluid inlet 209 and atleast one fluid conduit (not shown) formed through the base member 204and connecting the inlet 209 to the fluid volume above the membrane 208within inner basin 202. Similarly, an anolyte solution is provided tothe fluid volume within the inner basin 202 that is below the membrane208 via at least one of the fluid inlets 209 and a fluid conduit 212.The anolyte solution generally flows over the upper surface of the anode205 and is collected by a corresponding conduit 212 on the opposingside. Additionally, the fluid conduit 212 may also be positioned influid communication with the fluid volume above the diffusion member 210and below the membrane 208.

In this embodiment the copper ions in the anolyte solution aretransferred through the diffusion member 210 and through the membrane208 toward the substrate being plated during the electrolytic platingprocess. However, plating additives and contaminants that may accumulatein the catholyte solution are not permitted by virtue of the cationicmembrane properties that do not allow these constituents to pass throughthe membrane 208 in the direction of the anode. The perpendicular lineresistance between the anode 205 and the substrate being plated (whichis generally positioned parallel to the anode during plating) isgenerally constant at all points across the anode 205, and further, as aresult of the positioning of the diffusion member 210 in the anolyte,the resistance is substantially higher than in conventional platingcells.

In the embodiment of the invention illustrated in FIG. 3, the fluid flowpattern is similar to the fluid flow pattern for the embodimentillustrated in FIG. 2. Additionally, the perpendicular line resistanceis again equal across all points on the anode surface, as the proportionof the diffusion member 310 thickness to the distance the membrane 308is away from the anode remains constant for all points across the anode.As such, the diffusion member 310 may be wedge shaped and the membrane308 may be positioned at a tilt angle. This configuration minimizesbubble formation at the surface of the substrate being plated, reducesthe terminal effect, and allows for an electrolytic plating process tobe conducted on thinner seed layers than possible in conventionalplating cells where the diffusion member is positioned in the catholyte.In both of the embodiments illustrated in FIGS. 2 and 3, the anolytefluid conduits 212 may be configured to supply the anolyte solution tothe fluid volume both above the diffusion member 210, 310 and below thediffusion member 210, 310.

The operational characteristics of the embodiment of the inventionillustrated in FIG. 4 are slightly different from previous embodimentsas a result of the positioning of the respective membrane stacks 420,430, 440. The respective membrane stacks 420, 430, 440 generally includea larger porous filter membrane positioned below a smaller porous filtermembrane, wherein the larger porous membrane is generally positionedadjacent either the ionic membrane 408 or the anode 405, for example.Generally speaking, the positioning of the membrane stack 420 above theionic membrane 408 allows copper ions coming out of the membrane 408(ions transferring from the catholyte to the anolyte) to be moved awayfrom the surface of the ionic membrane 408, thus reducing passiviationat the membrane 408 surface and increasing plating rates. Moreparticularly, the catholyte fluid drain 425 positioned in fluidcommunication with the volume between the first membrane 421 and thecationic membrane 408 operates to generate a catholyte fluid flowexiting the fluid volume between the first membrane 421 and the ionicmembrane 408. The exiting catholyte fluid flow generates a reducedpressure in the fluid volume between the first membrane 421 and theionic membrane 408, and as a result thereof, replacement catholyte ispulled through the membrane stack 420 and into the fluid volume betweenthe first membrane 421 and the ionic membrane 408. This fluid musttravel through the second membrane 422 and the first membrane 421 inorder to reach the fluid volume between the first membrane 421 and theionic membrane 408.

The second membrane stack 430 operates in a similar manner to the firstmembrane stack 420. More particularly, a first large porous membrane 427is positioned adjacent a lower surface of the ionic membrane 408 and asecond smaller porous membrane 428 is positioned adjacent the firstmembrane 427. The anolyte drain 428 operates to remove anolyte from thefluid volume between the lower surface of the ionic membrane 408 and thefirst membrane 427, which again generates a reduced pressure that pullsreplacement fluid into the volume. The replacement fluid, i.e., anolyte,is pulled from through the second membrane 428 and first membrane 427into the fluid volume between the first membrane 427 and the lowersurface of the ionic membrane 408. This configuration generally operatesto circulate the anolyte solution that is depleted of copper ions, i.e.,the anolyte solution adjacent the ionic membrane surface, away from thesurface of the ionic membrane 408. This provides a continual andsufficient supply of copper ions for transport through the ionicmembrane 408, which in turn operates to prevent the cell voltage fromrising as a result of a copper ion deficiency at the ionic membrane 408.

The third membrane stack 440 provides a similar function to the anode405 as membrane stacks 420, 430 do for the ionic membrane 408. Moreparticularly, the positioning of the larger porous first membrane 441adjacent the anode and the smaller porous second membrane 442 adjacentthe first porous membrane 441 operates to flush material away from thesurface of the anode 405. Specifically, the anolyte conduit 426 is influid communication with the fluid volume between the first membrane 441and the anode 405 and is configured to remove anolyte therefrom. Assuch, a negative pressure is generated in the fluid volume between thefirst membrane 441 and the anode 405, which operates to pull anolyteinto the fluid volume. The anolyte being pulled into the fluid volumetravels through the second membrane 442 and the first membrane 441 toreach the fluid volume, and is then removed therefrom by the anolyteconduit 426, thus generating an anolyte circulation loop. The largerporous membrane 441 is similar in construction, thickness, and pore sizeto the first membrane 421 of first stack 420, and the second membrane442 is similar in construction, thickness, and pore size to the secondmembrane 422 of the first membrane stack 420.

The third membrane stack 440 generally operates to pull sludge thatforms on the surface of the anode away from the anode surface, whichreduces the need to tilt the plating cell in order to urge the sludge toflow into the anode slots for removal from the anode surface.Additionally, this flow pattern also operates to pull the copper richanolyte away from the anode surface and circulate the copper richanolyte into the bulk anolyte solution volume, which allows higherplating rates that do not require increased fluid flow in the platingcell. Additional benefits of the third membrane stack 440 positioned onor immediately above the anode 405 include reduced anode passiviation atcurrent densities of less than about 80 mA/cm², reduced bowing of theionic membrane 408 as a result of increased fluid pressure, which alsominimizes center thin plating challenges, elimination of metallizationof the ionic membrane 408, and increased anode life, as a slotted anodeconfiguration, such as the anode 205 illustrated in FIG. 2, may bereplaced with a solid disk shaped anode having a longer processing life.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, wherein the scope thereof isdetermined by the claims that follow.

1. An electrochemical plating cell, comprising: a fluid basin having afluid inlet and a fluid outlet; a membrane positioned across the fluidbasin, the membrane separating the fluid basin into a catholyte volumeand an anolyte volume; an anode positioned in the anolyte volume; and anelectrically resistive fluid permeable diffusion member positionedacross the anolyte volume.
 2. The plating cell of claim 1, wherein themembrane comprises a cationic membrane.
 3. The plating cell of claim 2,wherein the diffusion member comprises a varying thickness disk shapedmember.
 4. The plating cell of claim 3, wherein the diffusion membercomprises a porous ceramic disk.
 5. The plating cell of claim 1, whereinthe diffusion member comprises a disk shaped member having asubstantially uniform thickness.
 6. The plating cell of claim 3, whereinthe diffusion member comprises a disk shaped member having a firstthickness on a first edge of the disk shaped member and a secondthickness on a second opposing edge of the disk shaped member, the firstthickness being different from the second thickness.
 7. The plating cellof claim 6, wherein a central plane of the diffusion member ispositioned substantially parallel to an upper surface of the anode. 8.The plating cell of claim 7, wherein the membrane is positioned at anangle across the fluid basin with respect to the upper surface of theanode.
 9. The plating cell of claim 8, wherein the membrane ispositioned at a first distance from the anode surface on a thin side ofthe diffusion member and at a second distance from the anode surface ona thick side of the diffusion member, the first distance being greaterthan the second distance.
 10. The plating cell of claim 3, wherein thediffusion member is positioned substantially parallel to an uppersurface of the anode.
 11. An electrochemical plating cell, comprising: acell body defining a fluid processing volume and having an openingconfigured to receive a substrate for processing; a cationic membranepositioned across the fluid processing volume and separating the fluidprocessing volume into a catholyte volume and an anolyte volume; ananode positioned in the anolyte volume; and an electrically insulativefluid permeable diffusion member positioned across the fluid processingvolume between the anode and the cationic membrane.
 12. The plating cellof claim 11, wherein the cationic membrane is positioned parallel to anupper surface of the anode.
 13. The plating cell of claim 11, whereinthe cationic membrane is positioned at an angle with respect to an uppersurface of the anode.
 14. The plating cell of claim 11, wherein thediffusion member comprises a disk shaped member having a substantiallyuniform thickness.
 15. The plating cell of claim 13, wherein thediffusion member comprises a disk shaped member having a first thicknesson a first edge and a second thickness on a second edge, the firstthickness being greater than the second thickness.
 16. The plating cellof claim 15, wherein the cationic membrane is positioned a firstdistance from the anode at a position in the fluid processing volumeadjacent the first side and a second distance from the anode at aposition in the fluid processing volume adjacent the second side,wherein the first distance is less than the second distance.
 17. Theplating cell of claim 13, wherein the angle is between about 5° andabout 15°.
 18. The plating cell of claim 11, further comprising ananolyte fluid inlet and an anolyte fluid outlet in fluid communicationwith the anolyte volume, and a catholyte fluid inlet and a catholytefluid outlet in fluid communication with the catholyte volume.
 19. Theplating cell of claim 18, wherein the anolyte fluid inlet is positionedto deliver an anolyte solution to a volume below the diffusion memberand to a volume above the diffusion member.
 20. An electrochemicalplating cell, comprising: a fluid basin having an opening configured toreceive a substrate for processing; a copper anode positioned in a lowerportion of the fluid basin; a porous electrically insulative diffusionmember positioned across the fluid basin at a position between the anodeand the opening; a cationic membrane positioned across the fluid basinat a position between the diffusion member and the opening.
 21. Theplating cell of claim 20, wherein the diffusion member is wedge shapedand has a central plane that is substantially parallel to an uppersurface of the anode.
 22. The plating cell of claim 21, wherein thecationic membrane is positioned at a tilt angle with respect to theupper surface of the anode.
 23. The plating cell of claim 22, whereinthe tilt angle is proportional to a slope of the diffusion member. 24.The plating cell of claim 20, wherein the diffusion member is diskshaped member having a substantially uniform thickness.
 25. The platingcell of claim 24, wherein the cationic membrane is positioned parallelto the diffusion member.